CN115332738A

CN115332738A - Electrochemical device and electricity utilization device

Info

Publication number: CN115332738A
Application number: CN202210962684.8A
Authority: CN
Inventors: 李学成
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2022-05-09
Filing date: 2022-05-09
Publication date: 2022-11-11
Anticipated expiration: 2042-05-09
Also published as: CN115332738B; CN114583408B; CN114583408A

Abstract

An electrochemical device and a power utilization device are disclosed. The electrochemical device comprises an electrode component and a tab, wherein the tab extends out of the electrode component and comprises a first conducting layer and a second conducting layer which are overlapped, the first conducting layer is electrically connected with the electrode component, and the first conducting layer and the second conducting layer are electrically conducted; wherein the tensile strength of the second conductive layer is greater than the tensile strength of the first conductive layer. The electrode lug of the electrochemical device has good conductivity and tensile strength, and the service life of the product is prolonged.

Description

Electrochemical device and electricity utilization device

The present application is a divisional application based on the inventions of application No. 202210495814.1, application date 2022, 05.09.h, ningde New energy science and technology Co., ltd, entitled "electrochemical device and electric device".

Technical Field

The application relates to the technical field of electric energy storage, in particular to an electrochemical device and an electric device.

Background

An electrochemical device is a device that converts external energy into electrical energy and stores the electrical energy in the device to supply power to external electric equipment (such as portable electronic equipment) when necessary. In the technical development of the electrochemical device, besides improving the energy density, the service life of the electrochemical device is a considerable problem, and particularly, the service life of the electrochemical device is greatly influenced by whether the electrode lug can normally work after the electrochemical device is collided.

In summary, it is desirable to design an electrochemical device and an electric device to solve the above-mentioned technical problems.

Disclosure of Invention

The embodiment of the application provides an electrochemical device and an electric device, wherein, the electrode lug of the electrochemical device has good conductivity and tensile strength, and the service life of the product is prolonged.

In a first aspect, embodiments of the present application provide an electrochemical device, including:

an electrode assembly;

the electrode assembly comprises an electrode assembly, a lug and a conductive layer, wherein the electrode lug extends out of the electrode assembly and comprises a first conductive layer and a second conductive layer which are overlapped;

wherein the tensile strength of the second conductive layer is greater than the tensile strength of the first conductive layer.

In some embodiments, the electrode assembly includes a first end and a second end, the first end and the second end are opposite to each other along a first direction, the tab is bent and extended from the first end to a direction close to a central axis of the electrode assembly, the second conductive layer is disposed at least on a side of the first conductive layer close to the electrode assembly, and the central axis extends perpendicular to the first direction.

In some embodiments, the second conductive layer covers the first conductive layer, or the first conductive layer covers the second conductive layer.

In some embodiments, the number of the first conductive layers is two, and the two first conductive layers are respectively arranged on two opposite sides of the second conductive layer along the thickness direction of the first conductive layers.

In some embodiments, the tab further comprises a conductive composite layer disposed between the first conductive layer and the second conductive layer, and the first conductive layer and the second conductive layer are hot rolled to form the conductive composite layer.

In some embodiments, the tab further includes a conductive adhesive layer disposed between the first conductive layer and the second conductive layer, the conductive adhesive layer being adhered to and electrically connecting the first conductive layer and the second conductive layer.

In some embodiments, the conductive adhesive layer includes a base material and conductive particles mixed in the base material.

In some embodiments, the material of the substrate is one or more of ethyl cyanoacrylate, epoxy, acrylate, and polyurethane.

In some embodiments, the melting temperature of the conductive adhesive layer is greater than or equal to 200 ℃.

In some embodiments, the surface of the second conductive layer is at least partially a passivated surface.

In some embodiments, the first conductive layer has a thickness of 10 to 100 μm and the second conductive layer has a thickness of 5 to 30 μm.

In some embodiments, the first conductive layer is an aluminum layer and the second conductive layer is a steel layer.

In some embodiments, the electrochemical device further comprises an insulator coupled to the tab, the tab having a peel strength from the insulator of greater than 1.5N/mm.

In a second aspect, an embodiment of the present application further provides a battery, including:

a housing having an accommodating space;

according to the electrochemical device provided by the first aspect, the electrochemical device is accommodated in the accommodating space.

In a third aspect, embodiments of the present application further provide an electric device, including an electrochemical device provided according to the first aspect, the electrochemical device being configured to provide electrical energy.

Compared with the prior art, in the electrochemical device and the electricity utilization device provided by the embodiment of the application, the second conducting layer has higher tensile strength, so that the second conducting layer can enhance the overall strength of the tab, and the tab has better tensile resistance and bending resistance; the tensile strength of the second conducting layer is larger than that of the first conducting layer, so that when the first conducting layer in the tab is broken, cracked and other damaged conditions exist, the second conducting layer can still conduct the electrode assembly and external parts, the tab still has a conducting function, the electrochemical device still can participate in charging and discharging work, and the service life of the electrochemical device is prolonged.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and it is apparent that the drawings described below are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings.

Fig. 1 is a schematic perspective view of an electrochemical device according to an embodiment of the present application;

fig. 2 is a schematic cross-sectional structure view of a tab provided in an embodiment of the present application;

FIG. 3 is a schematic structural view of an electrochemical device according to another embodiment of the present application;

fig. 4 is a schematic cross-sectional structural view of a tab provided in an embodiment of the present application;

fig. 5 is a schematic cross-sectional structural view of a tab provided in an embodiment of the present application;

fig. 6 is a schematic cross-sectional structure view of a tab provided in an embodiment of the present application;

fig. 7 is a schematic cross-sectional structure view of a tab provided in an embodiment of the present application;

fig. 8 is a schematic cross-sectional structure view of a tab provided in an embodiment of the present application;

fig. 9 is a schematic cross-sectional structure view of a tab provided in an embodiment of the present application;

fig. 10 is a schematic perspective view of a battery according to an embodiment of the present application.

In the drawings:

a battery 100; an electrochemical device 10; a housing 20; a housing space 201;

an electrode assembly 1; a first end portion 11; a second end portion 12; 2, a tab; a first conductive layer 21; a second conductive layer 22; a conductive composite layer 23; a conductive adhesive layer 24; an insulating member 3.

Detailed Description

Features of various aspects of the present application and exemplary embodiments will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present application by illustrating examples thereof.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The embodiments will be described in detail below with reference to the accompanying drawings.

In one aspect, the present application provides an electrochemical device. For a better understanding of the technical solutions and effects of the present application, specific embodiments will be described in detail below with reference to the accompanying drawings.

Referring to fig. 1 and 2, an electrochemical device 10 includes an electrode assembly 1 and a tab 2, the tab 2 extending from the electrode assembly 1, the tab 2 including a first conductive layer 21 and a second conductive layer 22 stacked on each other, the first conductive layer 21 being electrically connected to the electrode assembly 1, the first conductive layer 21 and the second conductive layer 22 being electrically connected to each other; wherein, the tensile strength of the second conductive layer 22 is greater than that of the first conductive layer 21.

The electrochemical device 10 provided in the present application may be applied to a lithium ion battery, a lithium sulfur battery, a sodium lithium ion battery, a sodium ion battery, a magnesium ion battery, or the like, and the present application is not limited thereto. When the electrochemical device 10 is applied to a battery, the electrochemical device 10 is soaked in an electrolyte, at least two electrochemical devices 10 can be respectively used as a positive electrode plate and a negative electrode plate, the active material-containing parts of the positive electrode plate and the negative electrode plate form an electrode assembly 1 of the electrochemical device 10, and the inactive material-free parts of the positive electrode plate and the negative electrode plate form tabs 2. During the charge and discharge of the battery, the positive electrode active material and the negative electrode active material react with the electrolyte. The tab 2 is used to connect electrode terminals to form a current loop.

The first conductive layer 21 may be electrically connected to the electrode assembly 1 by welding, the second conductive layer 22 electrically connected to the first conductive layer 21 may not be directly connected to the electrode assembly 1, and the second conductive layer 22 is electrically connected to the electrode assembly 1 through the first conductive layer 21. The first conductive layer 21 and the second conductive layer 22 may also both have a direct connection relationship with the electrode assembly 1, so that the second conductive layer 22 may be electrically connected to the electrode assembly 1 without passing through the first conductive layer 21. It is understood by those skilled in the art that the material of the first conductive layer 21 and the material of the second conductive layer 22 may be a single substance or a mixture. When the first conductive layer 21 and the second conductive layer 22 are both a mixture, the compositions of the first conductive layer 21 and the second conductive layer 22 may be different or the same. In the case where the first conductive layer 21 and the second conductive layer 22 have the same composition, one skilled in the art can adjust the ratio of the components so that the second conductive layer 22 exhibits better tensile strength than the first conductive layer 21.

In the case where the electrochemical device 10 has a complete structure without breakage, the electrode assembly 1 may form a current loop with an external part through the first and second

conductive layers

21 and 22 in the tab 2 at the same time, and in particular, may form a current loop with an electrode terminal through the first and second

conductive layers

21 and 22 at the same time. Under the condition that the electrochemical device 10 is impacted and bent by external force, the tensile strength of the first conductive layer 21 is smaller than that of the second conductive layer 22, so that the second conductive layer 22 has better tensile resistance and bending resistance compared with the first conductive layer 21, and the tensile resistance and bending resistance of the first conductive layer 21 are improved under the supporting action of the second conductive layer 22; when the first conductive layer 21 in the tab 2 has a breakage condition such as a fracture or a crack, the second conductive layer 22 can still connect the electrode assembly 1 and an external part, so that the tab 2 still has a conductive function, and the electrochemical device 10 can still participate in charging and discharging operations.

In the electrochemical device 10 provided by the present application, the second conductive layer 22 has a greater tensile strength, so that the second conductive layer 22 can enhance the overall strength of the tab 2, and the tab 2 has better stretch resistance and bending resistance; by setting the tensile strength of the second conductive layer 22 to be greater than the tensile strength of the first conductive layer 21, the first conductive layer 21 in the tab 2 has breakage conditions such as fracture and crack, the second conductive layer 22 can still conduct the electrode assembly 1 and external parts, so that the tab 2 still has a conductive function, the electrochemical device 10 can still participate in charging and discharging operations, and the service life of the electrochemical device 10 is prolonged.

Please refer to fig. 3,. And is vertical.

The electrode assembly 1 may be formed by winding a positive electrode tab and a negative electrode tab along the central axis L, and the tab 2 is connected to the first end 11 of the electrode assembly 1 and extends outward, so that the tab 2 can be conveniently connected to other components. The tab 2 connected with the positive pole piece and the tab 2 connected with the negative pole piece are both bent and extended towards the direction close to the central axis L, so that the tab 2 connected with the positive pole piece and the tab 2 connected with the negative pole piece are conveniently connected to the same insulation structure. The second conductive layer 22 is at least disposed on one side of the first conductive layer 21 close to the electrode assembly 1, so that the second conductive layer 22 can support the first conductive layer 21, and at the same time, the stress of the first conductive layer 21 when being impacted or squeezed is dispersed, which is beneficial to preventing the first conductive layer 21 from being broken and prolonging the service life of the tab 2.

In some embodiments, the electrochemical device 10 further comprises an insulator 3 coupled to the tab 2, and the peel strength of the tab 2 from the insulator 3 is greater than 1.5N/mm at 85 ℃ for 4 hours. It will be appreciated by those skilled in the art that the peel strength of first conductive layer 21 from insulator 3, and the peel strength of second conductive layer 22 from insulator 3, may not be the same. The insulator 3 is used for insulating the tab 2, the tab 2 connected with the positive pole piece and the tab 2 connected with the negative pole piece can be connected to the same insulator 3, and the insulator 3 is used for insulating the two. The external surface of the tab 2 may be roughened to increase the peel strength between the tab 2 and the insulator 3.

Referring to fig. 4, in some embodiments, the second conductive layer 22 covers the first conductive layer 21. Referring to fig. 5, in other embodiments, the first conductive layer 21 covers the second conductive layer 22. That is, one of the first conductive layer 21 and the second conductive layer 22 is wrapped around the other, so that one of the first conductive layer and the second conductive layer is completely protected and isolated from external gas, liquid and the like to a certain extent, thereby reducing or avoiding the corrosion, oxidation and the like of the conductive layer located at the center.

Under the condition that the second conductive layer 22 covers the outer side of the first conductive layer 21, the second conductive layer 22 can support the first conductive layer 21 from the periphery of the first conductive layer 21, so that the first conductive layer 21 is not easy to break, crack and other damage phenomena. In the case that the first conductive layer 21 is coated outside the second conductive layer 22, the first conductive layer 21 has more exposed outer surfaces, which facilitates the connection of the electrode assembly 1 and external parts via the first conductive layer 21 by the tab 2.

Referring to fig. 6, in other embodiments, the number of the first conductive layers 21 is two, and the two first conductive layers 21 are respectively disposed on two opposite sides of the second conductive layer 22 along the thickness direction of the first conductive layer 21.

It will be understood by those skilled in the art that the electrode assembly 1 is generally in a sheet-type structure and thus the tabs 2 are also generally in a sheet-type structure in order to coat more active materials on the electrode assembly 1 to perform chemical reactions, thereby improving the overall energy density of the fabricated battery. Accordingly, the thickness direction of the first and second

conductive layers

21 and 22 is the thickness direction of the tab 2. The two first conductive layers 21 are respectively disposed on two opposite sides of the second conductive layer 22, i.e. a three-layer stacked structure of the first conductive layer 21, the second conductive layer 22 and the first conductive layer 21 is formed. The first conductive layer 21 and the second conductive layer 22 may be stacked together by pressing, attaching, or the like. Also, the first conductive layer 21 of the tab 2 has a more exposed outer surface, facilitating the connection of the tab 2 to the electrode assembly 1 and external parts through the first conductive layer 21.

One skilled in the art can also set the two first conductive layers 21 to different thicknesses as desired. For example, when the tab 2 is assembled into a battery in a state of being bent in a certain direction, the thickness of the first conductive layer 21 positioned at the outer side may be set to be greater than that of the first conductive layer 21 positioned at the inner side, so that the first conductive layer 21 positioned at the outer side can withstand greater bending stress.

Referring to fig. 7, the tab 2 further includes a conductive composite layer 23 disposed between the first conductive layer 21 and the second conductive layer 22, and the first conductive layer 21 and the second conductive layer 22 are hot-rolled to form the conductive composite layer 23.

Hot rolling (hot rolling) is rolling performed at a temperature equal to or higher than the recrystallization temperature of the material. The first material of the first conductive layer 21 and the second material of the second conductive layer 22 may be prepared into sheet-shaped rolled materials, and then the two rolled materials are stacked together and passed through a hot rolling mill, and the hot rolling mill applies pressure to the two materials to compress and deform the two materials into a whole. Under the pressure, the opposite surfaces of the first material and the second material are pressed against each other to form a material mixed region in which the first material and the second material are mixed, that is, the conductive composite layer 23. It will be understood by those skilled in the art that the conductive composite layer 23 does not have a distinct line of demarcation with the first and second

conductive layers

21 and 22, respectively. The conductive composite layer 23 formed by hot rolling is beneficial to ensuring that the first conductive layer 21 and the second conductive layer 22 are closely connected, and avoids that a gap exists between the first conductive layer 21 and the second conductive layer 22 due to the action of external force, temperature and the like, the supporting effect of the second conductive layer 22 on the first conductive layer 21 is influenced, and the electric path effect between the first conductive layer 21 and the second conductive layer 22 is influenced to a certain extent.

Referring to fig. 8 and 9, the tab 2 further includes a conductive adhesive layer 24 disposed between the first conductive layer 21 and the second conductive layer 22, wherein the conductive adhesive layer 24 is adhered to and electrically connects the first conductive layer 21 and the second conductive layer 22.

The conductive adhesive layer 24 is made of a material having both adhesive and electrical conductivity, and may be specifically a conductive glue. The conductive adhesive layer 24 may have a certain fluidity so as to change with the structural state of the tab 2 when bonding the first conductive layer 21 and the second conductive layer 22. The first conductive layer 21 and the second conductive layer 22 are bonded by the conductive adhesive layer 24, so that the connection stability of the first conductive layer 21 and the second conductive layer 22 can be improved.

The conductive adhesive layer 24 includes a base material and conductive particles mixed in the base material. The substrate is of a material having adhesive properties and the first and second

conductive layers

21, 22 are electrically conductive through one or more conductive particles in the substrate. Optionally, the material of the substrate is one or more of ethyl cyanoacrylate, epoxy resin, acrylate resin and polyurethane. Alternatively, the material of the conductive particles may be aluminum powder, silver powder, copper powder, iron powder, nickel powder, zinc powder, or the like. Those skilled in the art can select a suitable base material and conductive particles, and adjust the mixing ratio of the base material and the conductive particles, so that the conductive adhesive layer 24 having better conductivity and adhesion can be prepared. Alternatively, the adhesion of the conductive adhesive layer 24 is > 15N/8mm, and the peel strength of the first conductive layer 21 and the second conductive layer 22 is > 6N/15mm, so as to ensure that the first conductive layer 21 and the second conductive layer 22 can support each other and can be electrically conducted. Optionally, the peel strength of the conductive adhesive layer 24 and the first conductive layer 21 is greater than the peel strength of the first conductive layer 21 and the second conductive layer 22.

It will be appreciated by those skilled in the art that the conductive adhesive layer 24 also needs to have a better heat resistance because the tab 2 also needs to be electrically connected to other external parts and also needs to participate in other processing steps in the battery manufacturing process, for example, during the process of providing a sealing member at the tab 2 by ultrasonic welding, and during the process of connecting the tab 2 to a current collector by ultrasonic welding, in which the temperature of the tab 2 will far exceed room temperature. In some embodiments, the melting temperature of the conductive adhesive layer 24 is greater than or equal to 200 ℃, so as to ensure that the conductive adhesive layer 24 is not denatured during the subsequent processing of the electrochemical device 10, thereby avoiding the delamination phenomenon in the tab 2.

Since the tab 2 inevitably comes into contact with the electrolyte, the material of the first conductive layer 21, the material of the second conductive layer 22, and the material of the conductive adhesive layer 24 are also required to be resistant to the electrolyte. In some embodiments, the outer surfaces of the first conductive layer 21 and the second conductive layer 22 are passivated to improve the corrosion resistance of the tab 2 in the electrolyte. In other embodiments, only the outer surface of the tab 2 is passivated. For example, in one embodiment, the tab 2 includes only one first conductive layer 21 and one second conductive layer 22, and only the surfaces of the first conductive layer 21 and the second conductive layer 22 facing away from each other are passivated. For another example, in another embodiment, the tab 2 includes two first conductive layers 21 and one second conductive layer 22, the first conductive layers 21 are disposed on two sides of the second conductive layer 22, and passivation is performed only on one side of the first conductive layer 21 away from the second conductive layer 22. Only a part of the surfaces of the first conductive layer 21 and the second conductive layer 22 are passivated, thereby reducing the manufacturing cost.

In another embodiment, the surface of the second conductive layer 22 is at least partially a passivated surface. It will be appreciated by those skilled in the art that the second conductive layer 22 may also be passivated to improve the corrosion resistance of the second conductive layer 22 in the electrolyte.

In some embodiments, the first conductive layer 21 is an aluminum layer and the second conductive layer 22 is a steel layer. The tensile strength of the steel layer with the thickness of 50 mu m is more than or equal to 300N/m and is higher than that of the aluminum layer with the same thickness. Compared with the pole lug 2 made of only aluminum, the pole lug 2 with the same thickness and added with the steel layer has better tensile strength. Compared with the electrode lug 2 prepared only by aluminum, the electrode lug 2 added with the steel layer is thinner in the electrode lug 2 with the same tensile strength, so that a liquid leakage channel can be avoided to a certain extent when the sealant is ultrasonically welded, and the product quality is improved.

Optionally, the surface of the steel layer may be passivated with a chromium solution to improve the resistance of the steel layer to electrochemical corrosion.

In some embodiments, the thickness of the first conductive layer 21 is 10 to 100 μm, and the thickness of the second conductive layer 22 is 5 to 30 μm. The thickness of the second conductive layer 22 is less than at least half of the thickness of the first conductive layer 21. As will be understood by those skilled in the art, when there are a plurality of first conductive layers 21, the thickness of each first conductive layer 21 may be correspondingly reduced such that the thickness of the entire tab 2 is within a preset range. Alternatively, the number of the first conductive layers 21 is two, and the thickness of the first conductive layers 21 is 10 to 50 μm. The first conducting layer 21 and the second conducting layer 22 which are too thick can improve the overall thickness of the tab 2, increase the probability of generating a liquid leakage channel during ultrasonic welding of sealant to a certain extent, and reduce the product quality; the first conductive layer 21 and the second conductive layer 22, which are too thin, may cause insufficient tensile resistance of the entire tab 2, and may be easily broken by an external force.

To verify the beneficial effects of the above embodiments of the tab 2, please refer to the following embodiments.

Example 1

An aluminum foil with a thickness of 80um and a steel foil with a thickness of 20um are fixed together by hot rolling to prepare a metal band.

Example 2

And taking an aluminum foil with the thickness of 75um and a steel foil with the thickness of 15um, and bonding and fixing the aluminum foil and the steel foil together through conductive glue with the thickness of 10um to prepare the metal band. The conductive glue is made of epoxy resin and aluminum powder.

Example 3

Aluminum foil with the thickness of 40um and steel foil with the thickness of 20um are taken, and the steel foil is fixed between two layers of aluminum foils through hot rolling to prepare the metal band.

Example 4

And taking the aluminum foil with the thickness of 30um and the steel foil with the thickness of 20um, and bonding and fixing the steel foil between two layers of aluminum foils through the conductive glue with the thickness of 10um to prepare the metal band. The conductive glue is made of epoxy resin and aluminum powder.

Example 5

Aluminum foil with the thickness of 90um and steel foil with the thickness of 10um are fixed together through hot rolling to prepare a metal belt.

Example 6

And taking the aluminum foil with the thickness of 80um and the steel foil with the thickness of 10um, and bonding and fixing the aluminum foil and the steel foil together by using the conductive glue with the thickness of 10um to prepare the metal belt. The conductive glue is made of epoxy resin and aluminum powder.

Comparative example 1

An aluminum foil with the thickness of 100um is taken to prepare a metal belt.

The metal strips prepared in examples 1 to 6 and comparative example 1 were cut into strips 15mm wide and 150mm long to be subjected to a tensile test and a flow capacity test. In the tensile test, the distance between the clamps for stretching the sample strips in the tensile machine is 100mm, and the stretching speed is 30mm/min. In the overcurrent capacity test, the lug overcurrent capacity = Tab _{Width of} *Tab _{Thickness of} *Tab _{Coefficient of current carrying} (ii) a MetalWith current capability = sum of current capabilities of different metal layers. Wherein Tab represents a Tab, and the current-carrying coefficient of Al material is 5A/mm ² The current-carrying coefficient of the Cu material is 8A/mm ² The current-carrying coefficient of the Ni material is 2A/mm ² The current-carrying coefficient of steel is 3.2A/mm ² The current-carrying coefficient of the conductive glue is 0.08-0.1A/mm ² . See table 1 for specific test results.

TABLE 1 tensile test results for metal strips

Group of	Preparation process	Thickness of	Tensile Strength (MPa)	Overcurrent capacity (A)
					Example 1	Hot rolling	100um	213	6.96
Example 2	Bonding of	100um	190	6.36
					Example 3	Hot rolling	100um	220	6.96
Example 4	Bonding	100um	202	5.49
					Example 5	Hot rolling	100um	135	7.23
Example 6	Bonding of	100um	130	6.49
					Comparative example 1	Is composed of	100um	74.7	7.5

Comparing examples 1 to 6 with comparative example 1, respectively, it can be seen that the metal strips with the addition of steel foil have better tensile strength and less influence on the flow-through capacity than metal strips made solely of aluminum foil. As can be seen from comparison between example 1 and example 2, the metal strips prepared from the aluminum foil and the steel foil both by hot rolling and by conductive adhesive layer have good overcurrent capacity and tensile strength. As can be seen from comparative examples 1 and 3, and comparative examples 2 and 4, the metal tape having a single-layer aluminum foil structure and the metal tape having a double-layer aluminum foil structure both had good flow capacity and tensile strength. It is understood from the comparison of examples 1 and 5 and the comparison of examples 2 and 6 that the tensile strength of the metal strip is greatly improved when the steel foil is thick, and the influence on the flow capacity is not large.

The metal strips prepared in examples 1 to 6 and comparative example 1 were cut into strips 15mm wide and 150mm long to be subjected to a bending test. And (3) bending the metal strip by 180 degrees in a room temperature environment, and recording the bending times of the aluminum foil or the steel foil in the metal strip. See table 2 for specific results.

Table 2 bending test results of metal strips

Group of	Preparation process	Thickness of	Number of times of fracture bending
				Example 1	Hot rolling	100um	198
Example 2	Bonding	100um	161
				Example 3	Hot rolling	100um	205
Example 4	Bonding of	100um	203
				Example 5	Hot rolling	100um	110
Example 6	Bonding	100um	108
				Comparative example 1	Is composed of	100um	50

Comparing examples 1 to 6 with comparative example 1, respectively, it can be seen that, compared with a metal strip prepared only from aluminum foil, the metal strip added with steel foil has greatly increased times of fracture and bending, has better bending resistance, and can reduce or avoid the problem of fracture and failure of the tab 2 caused by external force collision. As can be seen from comparison between examples 1 and 2, the aluminum foil and the steel foil were fixed by hot rolling or by a conductive adhesive layer, and the number of times of breaking and bending of the prepared metal strip was significantly increased as compared to comparative example 1. As can be seen from comparative examples 1 and 3, and comparative examples 2 and 4, both the metal tape having the single-layer aluminum foil structure and the metal tape having the double-layer aluminum foil structure have good bending resistance. It is understood from comparative examples 1 and 5 and comparative examples 2 and 6 that the increase in the number of times of breaking and bending is large when the steel foil is thick. In some cases, the aluminum foil of the metal strip breaks without the steel foil breaking, without affecting the electrical path state.

The strip prepared in example 2 was cut into strips 15mm wide and 150mm long for high temperature resistance testing. And adopting different welding temperatures to weld different metal strips, and testing whether a liquid leakage channel is generated between the sealing element and the metal strips, wherein the sealing element is made of polyethylene. And bending the welded metal strip by 90 degrees, placing the metal strip into electrolyte, and testing whether the aluminum foil and the steel foil in the metal strip are separated and delaminated. See table 3 for specific results.

TABLE 3 Heat and Corrosion resistance test results of the Metal strip

According to the experiment, the sealing element is welded at 200 ℃, a liquid leakage channel cannot be generated between the sealing element and the lug, and meanwhile, the lug is not layered, so that the lug provided by the application is proved to be processed at the welding temperature of 200 ℃ and corroded by electrolyte, and the conductive bonding layer can still effectively bond the first conductive layer and the second conductive layer. When the welding temperature is above 220 ℃, the phenomenon that the sealing element is slightly scalded begins to occur, but the phenomenon of delamination still does not occur in the tab, and the fact that the conductive bonding layer can still effectively bond the first conductive layer and the second conductive layer is proved.

In a second aspect, the present application also provides a battery. Referring to fig. 10, a battery 100 includes a housing 20 having a receiving space 201, and the electrochemical device 10 provided by the first aspect, wherein the electrochemical device 10 is received in the receiving space 201.

At least two electrochemical devices 10 are respectively used as a positive electrode plate and a negative electrode plate, and the positive electrode plate and the negative electrode plate can be disposed in the casing 20 in a winding manner or a lamination manner. The plurality of batteries 100 may be connected in series or in parallel or in series-parallel to form a whole through which the batteries are charged and discharged, wherein the series-parallel connection means that the plurality of batteries 100 are connected in series or in parallel.

The structure of the electrochemical device 10 in the battery 100 can be referred to the electrochemical device 10 provided in the above embodiments, and will not be described herein.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

In order to verify the advantages of the above embodiments of the tab 2 and the battery 100 including the tab 2, please refer to the following embodiments in combination.

Example 7

1) Bonding an aluminum foil with the thickness of 60um and a steel foil with the thickness of 20um together through conductive glue to prepare a tab, wherein the thickness of the conductive glue is 10um, the aluminum foil is used as a first conductive layer, and the steel foil is used as a second conductive layer;

2) The prepared tabs were welded to an electrode assembly having a length of 91mm, a width of 66mm and a thickness of 6.0mm to prepare an electrochemical device.

Comparative example 2

1) Taking an aluminum foil with the thickness of 90um to prepare a tab;

2) The prepared tabs were welded to an electrode assembly 91mm long, 66mm wide, and 6.0mm thick to prepare an electrochemical device.

Comparative example 2 is different from example 7 in that the tab of comparative example 2 is made of only aluminum foil, and the tab of example 7 is made by bonding aluminum foil and steel foil through a conductive adhesive layer.

Example 8

2) The prepared tabs were welded to an electrode assembly having a length of 87mm, a width of 64mm and a thickness of 4.8mm to prepare an electrochemical device.

Example 7 differs from example 8 in that the electrode assemblies thereof differ in size.

Comparative example 3

1) Taking an aluminum foil with the thickness of 90um to prepare a tab;

Comparative example 3 is different from example 8 in that the tab of comparative example 3 is made of only aluminum foil and the tab of example 8 is made by bonding aluminum foil and steel foil through a conductive adhesive layer.

The electrochemical devices prepared in example 7, example 8, comparative example 2 and comparative example 3 were assembled to make cells, each of which was set to 10 replicates. The side of the electrode assembly close to the tab was faced to the steel plate, and the battery was placed from a height of 10cm and dropped, and repeated 5000 times. The voltage and internal resistance were measured for the cell every 1000 dips. And in the testing process, the appearance of the battery core is checked, and if the battery has abnormal conditions such as liquid leakage, ignition and the like, the battery stops continuously falling. And disassembling the battery cell after the drop test is completed, and counting the proportion of aluminum foil fracture in the tab.

Referring to table 4, the ratio of aluminum foil breakage in the battery subjected to the drop test is shown.

TABLE 4 aluminum foil fracture ratio

Group of	Fracture ratio of aluminum foil
		Example 7	0/10
Comparative example 2	7/10
		Example 8	0/10
Example 8	0/10

As can be seen from Table 4, the tab with the steel foil has better anti-collision capacity, and the fracture ratio of the aluminum foil can be greatly reduced.

In a third aspect, the present application also provides an electric device comprising the electrochemical device provided in the first aspect, wherein the electrochemical device is used for providing electric energy.

Specific product types of the electric device include, but are not limited to, a mobile terminal, a smart garment, an electric tool, an electric car, a mobile power supply, and the like.

Because the battery has the beneficial effects, the electric device has higher use safety and reliability and longer service life.

In addition, the term "and/or" herein is only one kind of association relationship describing an associated object, and means that there may be three kinds of relationships, for example, a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

It should be understood that in the embodiment of the present application, "B corresponding to a" means that B is associated with a, from which B can be determined. It should also be understood that determining B from a does not mean determining B from a alone, but may also be determined from a and/or other information.

While the invention has been described with reference to specific embodiments, the scope of the invention is not limited thereto, and those skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope of the invention, and these modifications or substitutions are intended to be included in the scope of the invention. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. An electrochemical device, comprising:

an electrode assembly;

a tab extending from the electrode assembly, the tab including a first conductive layer and a second conductive layer stacked on each other, the first conductive layer being electrically connected to the electrode assembly, the first conductive layer and the second conductive layer being electrically connected to each other, the second conductive layer being disposed at least on a side of the first conductive layer adjacent to a central axis of the electrode assembly;

2. The electrochemical device as claimed in claim 1, wherein the electrode assembly includes a first end portion and a second end portion, the first end portion and the second end portion are opposite to each other along a first direction, the tab is bent and extended from the first end portion to a direction close to a central axis of the electrode assembly, and the central axis extends perpendicularly to the first direction.

3. The electrochemical device as claimed in claim 2, wherein the tabs are at least partially bent in an arc shape protruding toward the central axis of the electrode assembly.

4. The electrochemical device of claim 1, wherein the second conductive layer is wrapped outside the first conductive layer, or the first conductive layer is wrapped outside the second conductive layer.

5. The electrochemical device according to claim 1, wherein the number of the first conductive layers is two, and the two first conductive layers are disposed on opposite sides of the second conductive layer in a thickness direction of the first conductive layers.

6. The electrochemical device as recited in any one of claims 1 to 5, wherein the tab further comprises an electrically conductive composite layer disposed between the first and second electrically conductive layers, the first and second electrically conductive layers being hot rolled to form the electrically conductive composite layer.

7. The electrochemical device as claimed in any one of claims 1 to 5, wherein the tab further comprises a conductive adhesive layer disposed between the first conductive layer and the second conductive layer, the conductive adhesive layer being adhered to and electrically connecting the first conductive layer and the second conductive layer.

8. The electrochemical device according to claim 7, wherein the conductive adhesive layer comprises a base material and conductive particles mixed in the base material.

9. The electrochemical device according to claim 8, wherein the material of the substrate is one or more of ethyl cyanoacrylate, epoxy resin, acrylate resin, and polyurethane.

10. The electrochemical device of claim 7, wherein the conductive adhesive layer has a melting temperature of 200 ℃ or higher.

11. The electrochemical device according to any of claims 1 to 5, wherein the surface of said second electrically conductive layer is at least partially a passivated surface.

12. The electrochemical device according to any one of claims 1 to 5, wherein the thickness of the first conductive layer is 10 to 100 μm, and the thickness of the second conductive layer is 5 to 30 μm.

13. The electrochemical device according to any one of claims 1 to 5, wherein the first electrically conductive layer is an aluminum layer and the second electrically conductive layer is a steel layer.

14. The electrochemical device according to any one of claims 1 to 5, further comprising an insulator coupled to the tab, wherein the tab has a peel strength from the insulator of greater than 1.5N/mm.

15. An electrical device comprising an electrochemical device according to any one of claims 1 to 14 for providing electrical energy.